Pesticide Residues and Exposure - ACS Publications - American

1 Trends in Chemical Residues Including Reentry Considerations JACK R. PLIMMER

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USDA, Organic Chemical Synthesis Laboratory, Agricultural Environmental Quality Institute, Agricultural Research Service, Beltsville, MD 20705 Preface: The development of synthetic organic pesticides passed through an accelerated phase during the decades following World War II. The discovery of the insecticidal activity of DDT, lindane and the organophosphates was followed rapidly by the introduction of carbamates and new organochlorine compounds. The 50's witnessed the introduction and widespread utilization of a variety of synthetic organic herbicides. The impact of these discoveries was dramatic. Human health benefited by the reduction of the incidence of malaria and other diseases carried by insect vectors. The World Health Organization proposed a campaign to control malaria in 1955 by using DDT and, by 1972, the disease had been eradicated in 36 countries (total population 710 million) (1). Selective herbicides eliminated much of the hand-weeding formerly needed in crop production and, by reducing the number of weeds that competed for water and nutrients, made possible substantial increases in crop yield. It also became possible to control undesirable vegetation in forests, on rights-of-way of highways or utilities, and in industrial areas without extensive use of hand-labor as in the past. The production of synthetic organic pesticides increased from an estimated 464,000 pounds in 1951 to an estimated 1.4 billion pounds in 1977 (2). Increases in production were followed by the recognition that such increased use of synthetic chemicals would be accompanied by extensive human and environmental impact. Pesticide use was regulated by federal and state governments, but continued evolution of the regulatory position has been necessitated by increasing usage and changes in patterns of use. The U.S. Environmental Protection Agency (U.S.E.P.A.), is responsible for the registration of pest control chemicals, but many aspects of pesticide use and handling also fall under the responsibility of a variety of Federal and State agencies. With rapid increase in pesticide This chapter not subject to U.S. copyright. Published 1982 American Chemical Society

In Pesticide Residues and Exposure; Plimmer, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.


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use, there has been a corresponding increase i n public a t t e n t i o n , and p u b l i c concern has often expressed i t s e l f i n l e g a l and p o l i t i c a l a c t i o n . However, i n many cases there has been inadequate i n f o r m a t i o n on which to base definitive r e g u l a t o r y a c t i o n . Data has accumulated s l o w l y , but during the 1950's and 60's there was a major e f f o r t to develop s e n s i t i v e and s e l e c t i v e techniques of a n a l y s i s and bioassay. Routes by which p e s t i c i d e s were transformed i n man, p l a n t s and the environment were e l u c i d a t e d . The q u a l i t a t i v e and q u a n t i t a t i v e aspects of d i s s i p a t i o n of p e s t i c i d e s i n the environment began t o be understood. During the 1970's much g r e a t e r a t t e n t i o n was focus sed on the i m p l i c a t i o n s of p e s t i c i d e use f o r human health. P e s t i c i d e use patterns and the philosophy of pest c o n t r o l have undergone e v o l u t i o n a r y changes i n response to these developments. Improvements i n a n a l y t i c a l techniques, p a r t i c u l a r l y the gas chromatograph, and the i n t e n s i f i c a t i o n of monitoring programs revealed that organochlorine insecticides were common contaminants of environmental samples. The l e v e l of DDT i n average U.S. i n h a b i t a n t s i n 1973 was 2.3 - 4.0 ppm and t h i s was accompanied by 4.3 - 8.0 ppm of DDE, a major degradation product. The corresponding f i g u r e s f o r the i n h a b i t a n t s of I n d i a were 16 ppm of DDT and 10 ppm of DDE ( 1 ) . Usage was higher i n I n d i a than the U.S., but the presence of low l e v e l s i n Eskimos, i n an area where DDT was not used, points to world-wide d i s t r i b u t i o n of residues (_3). Levels of DDT residues stored i n f a t a r e p r o p o r t i o n a l to i n t a k e , and the metabolism and e x c r e t i o n of DDT by mammals i s slow. Increased levels of DDT and other organochlorine i n s e c t i c i d e s residues i n man and the environment and the i n c r e a s i n g appearance of r e s i s t a n c e among i n s e c t s were among f a c t o r s that c o n t r i b u t e d to change i n use p a t t e r n s . The organophosphate i n s e c t i c i d e s l a r g e l y replaced organochlorines and were used on an i n c r e a s i n g s c a l e f o r c o n t r o l of i n s e c t s i n a g r i c u l t u r e and p u b l i c h e a l t h . In 1972, 10 m i l l i o n pounds of parathion and 40 m i l l i o n pounds of methyl parathion were used f o r i n s e c t c o n t r o l . Despite the high mammalian acute t o x i c i t y of most organophosphates, they have been widely accepted, but s t r i n g e n t safeguards are e s s e n t i a l to assure the s a f e t y of workers p o t e n t i a l l y exposed to these compounds. Although organophosphates now predominate as high-use i n s e c t i c i d e s , a v a r i e t y of chemicals of other f u n c t i o n a l types are used to c o n t r o l pests as h e r b i c i d e s , i n s e c t i c i d e s , f u n g i c i d e s , fumigants, d e f o l i a n t s e t c . Several of these are the source of p o t e n t i a l o p e r a t i o n a l hazards that must be addressed i n terms of worker p r o t e c t i o n and the n e c e s s i t y f o r a n a l y s i s of exposure and assessment of i t s e f f e c t s .


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P e s t i c i d e s may enter the body o r a l l y , through the s k i n ( d e r m a l l y ) , or through the r e s p i r a t o r y t r a c t . Some p e s t i c i d e s are so a c u t e l y t o x i c that t h e i r e f f e c t s appear a f t e r b r i e f exposure, and the most dangerous, i n terms of acute t o x i c i t y , include several organophosphate insecticides such as parathion. The r i s k of poisoning by dermal exposure to p a r a t h i o n i s great because i t i s e f f e c t i v e l y absorbed through the s k i n and i t s dermal t o x i c i t y approaches i t s o r a l t o x i c i t y . The dermal route of exposure i s l i k e l y to be one of the most significant for f i e l d workers, and contributors to this symposium have described a number of techniques f o r d i r e c t and i n d i r e c t a n a l y s i s of worker exposure. The primary b i o l o g i c a l e f f e c t s of the organophosphates are well defined. They act generally by inhibition of c h o l i n e s t e r a s e , an enzyme that i s involved i n the nerve t r a n s m i s s i o n process and i s present i n i n s e c t s and mammals. S u s c e p t i b i l i t y to an organophosphate i n s e c t i c i d e v a r i e s from species to species and from chemical to chemical. The symptoms of organophosphate poisoning are w e l l c h a r a c t e r i z e d i n humans. B i o l o g i c a l e f f e c t s that f o l l o w exposure i n c l u d e a l t e r a t i o n of c h o l i n e s t e r a s e l e v e l s i n plasma and c e l l , but the c o r r e l a t i o n of depressed c h o l i n e s t e r a s e l e v e l s with the appearance of c l i n i c a l symptoms i s poor, and normal l e v e l s of c h o l i n e s t e r a s e show great variability. However, c o r r e l a t i o n of mammalian c h o l i n e s t e r a s e levels with known doses of pesticides in statistically c o n t r o l l e d experiments may provide u s e f u l g u i d e l i n e s when the information is combined with the corresponding residue d i s s i p a t i o n data . Although acute c l i n i c a l symptoms may be r a r e l y observed f o l l o w i n g exposure to p e s t i c i d e s of low mammalian t o x i c i t y , i t i s a l s o important to monitor exposure l e v e l s . Such q u a n t i t a t i v e data may be especially important for epidemiological i n v e s t i g a t i o n s i n which a r e t r o s p e c t i v e study of causative f a c t o r s must be conducted. Without such data, conclusions can only be based on what may be unrepresentative sampling i n a d d i t i o n to q u a l i t a t i v e observations. Greater d i f f i c u l t i e s l i e i n assessing the e f f e c t s of long-term exposure to low l e v e l s of pesticides. Occupational exposure may be q u a n t i t a t i v e l y assessed, but the v a r i a t i o n s i n i n d i v i d u a l s u s c e p t i b i l i t y and the i n t e r a c t i o n of other f a c t o r s that a f f e c t h e a l t h must be considered i n the i n t e r p r e t a t i o n of e p i d e m i o l o g i c a l s t u d i e s . Most d i f f i c u l t are assessments of the e f f e c t s of long-term, lowl e v e l exposures that may occur i n the p o p u l a t i o n at large as a result of dietary intake or environmental contamination. Nevertheless, i t i s important to monitor the l e v e l s of environmental p o l l u t a n t s i n man and the food supply and to o b t a i n b a s e l i n e data that w i l l i n d i c a t e q u a l i t a t i v e and q u a n t i t a t i v e f l u c t u a t i o n s i n the content of these p o l l u t a n t s .


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We can expect that the controversy surrounding the l o n g term e f f e c t s of p e s t i c i d e s on man w i l l continue. The s i t u a t i o n i s i n c r e a s i n g l y complicated by the v a r i e t y of man-made chemicals i n t e n t i o n a l l y or u n i n t e n t i o n a l l y ingested during the human l i f e span. Although resources a v a i l a b l e to science and medicine are adequate to evaluate only l i m i t e d aspects of the problem, there is general agreement that measurements of human exposure represent an e s s e n t i a l f i r s t step to understanding. A p r i o r i t y f o r a g r i c u l t u r e i s to measure p e s t i c i d e residue l e v e l s encountered by those most d i r e c t l y a f f e c t e d by reason of their occupation; the workers engaged i n a g r i c u l t u r e and p e s t i c i d e manufacture. The l a t t e r present a somewhat d i f f e r e n t case because the f a c t o r y environment can be more s a t i s f a c t o r i l y c o n t r o l l e d than that of the f i e l d . P r o t e c t i v e measures f o r f i e l d workers, such as p r e s c r i p t i o n of r e e n t r y l e v e l s , o r other r e g u l a t o r y a c t i o n can only be i n t e l l i g e n t l y a p p l i e d i f there are s u f f i c i e n t data a v a i l a b l e from the f i e l d to describe the d u r a t i o n and extent of hazard. Because the Second American Chemical Congress was scheduled to be held i n C a l i f o r n i a , the t o p i c of worker-reentry was uppermost i n the minds of many p a r t i c i p a n t s and t h e i r c o n t r i b u t i o n s r e f l e c t c o n t r a s t i n g and c o n t r o v e r s i a l approaches to that problem. The m a j o r i t y of the symposium papers have addressed the problems of monitoring the exposure of f i e l d workers, although the scope of t h i s volume a l s o extends to problems of p e s t i c i d e s i n the p o p u l a t i o n a t large and to c o n s i d e r a t i o n s of i n d u s t r i a l hygiene. Several f a c t o r s a f f e c t the extent of hazard a s s o c i a t e d w i t h p e s t i c i d e use. The compound used, the type of f o r m u l a t i o n , and the a p p l i c a t i o n equipment a r e important. Acute t o x i c hazards of a c t i v e i n g r e d i e n t s may be c a t e g o r i z e d but i t must be recognized that the type of o p e r a t i o n w i l l a l s o i n f l u e n c e the hazard to the operator. For example, i t has been s t a t e d t h a t the a p p l i c a t i o n of p a r a t h i o n to f r u i t orchards by a power a i r b l a s t sprayer i s twice as hazardous to the operator as the a p p l i c a t i o n of dust t o row crops w i t h a boom duster ( 4 ) . The a g r i c u l t u r a l worker may be i n v o l v e d i n one of many o p e r a t i o n s , each i n v o l v i n g p a r t i c u l a r r i s k depending on the s i t u a t i o n and the d u r a t i o n of exposure. For t h i s reason, c a r e f u l a n a l y s i s of the o p e r a t i o n a l s i t e i s e s s e n t i a l and d i r e c t exposure measurements must be r e l e v a n t to working c o n d i t i o n s . C l i m a t i c c o n d i t i o n s and other environmental f a c t o r s w i l l a f f e c t the d i s s i p a t i o n of p e s t i c i d e r e s i d u e s . S o i l dust, r e s i d u a l p a r t i c l e s of a f o r m u l a t i o n , or other pesticide-contaminated m a t e r i a l s may e a s i l y be dislodged from f o l i a g e and the amount of d i s l o d g e a b l e m a t e r i a l present when workers enter the f i e l d i s an important guide to p o t e n t i a l hazard.


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P r o t e c t i o n r e q u i r e s a combination of approaches. There are a number of f a c t o r s that are i n t r i n s i c to the p h y s i o l o g i c a l and p s y c h o l o g i c a l makeup of the worker. Individual susceptibility and i n t e r a c t i o n with other b i o l o g i c a l s t r e s s e s w i l l vary from i n d i v i d u a l to i n d i v i d u a l . Personal hygiene and work h a b i t s a l s o vary. I t i s important that the worker f u l l y comprehends the nature of the hazards and the consequences of c a r e l e s s a c t i o n s or f a i l u r e to f o l l o w p r e s c r i b e d safe procedures. The a t t i t u d e s of workers and managers are important i n implementing working p r a c t i c e s that w i l l minimize r i s k s . The use of p r o t e c t i v e c l o t h i n g , the observation of o p e r a t i o n a l and r e g u l a t o r y g u i d e l i n e s and the observation of good work h a b i t s c o n t r i b u t e to safe p e s t i c i d e a p p l i c a t i o n . Access to r e g u l a r t r a i n e d medical advice and examination i s a l s o important. I f proper safeguards are to be maintained economically, i t i s e s s e n t i a l to define the extent of the hazard and i d e n t i f y the problem areas. Research i s needed to determine the s i t e s and d u r a t i o n of exposure and to measure the amounts of residues and t h e i r r a t e s of d i s s i p a t i o n . Such measurements can be made w i t h precision. The problem i s to use knowledge gained i n a p a r t i c u l a r s i t u a t i o n to provide g u i d e l i n e s or models which can be applied more generally to f i e l d operations. Such e x t r a p o l a t i o n s are c o n t r o v e r s i a l and they may a l s o be dangerous i f they a r e i n e r r o r . The symposium i n c l u d e s d e s c r i p t i o n s of techniques f o r measurement of exposure, and some c o n t r i b u t o r s i n d i c a t e the c o n t r o v e r s i a l aspects of s o l u t i o n s that have been proposed. The question of p r o t e c t i v e measures has been the subject of s e v e r a l s t u d i e s and r e p o r t s . In 1974 t h e F e d e r a l Working Group on Pest Management (F.W.G.P.M.) published the report of a task group on o c c u p a t i o n a l exposure to p e s t i c i d e s (_5)» The task group recommended that r e g i s t r a n t s should "develop and submit data s u f f i c i e n t to enable the r e s p o n s i b l e f e d e r a l agency t o promulgate safe reentry l e v e l s f o r each crop f o r which any new organophosphorus pesticide i s to be r e g i s t e r e d , i f the r e s p o n s i b l e agency has reason to b e l i e v e that exposure to f o l i a r residues may pose a significant hazard to a g r i c u l t u r a l workers". Additional recommendations included: the c o n s i d e r a t i o n of s i g n i f i c a n t geographical d i f f e r e n c e s i n the prevalence of the worker reentry problem; the n e c e s s i t y f o r h e a l t h s u r v e i l l a n c e systems; research to c l a r i f y f a c t o r s that i n f l u e n c e reentry i n t e r v a l s , such as the e f f e c t of personal hygiene, work p r a c t i c e s , degradation of f o l i a r r e s i d u e s ; and research to reduce r e l i a n c e on the use of chemical pest c o n t r o l systems. Research to reduce r e l i a n c e on the use of chemical pest c o n t r o l agents has received considerable support, and


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systems of i n t e g r a t e d pest management are e v o l v i n g i n which chemical p e s t i c i d e s may be more e f f i c i e n t l y used by techniques such as improved p r e d i c t i o n of pest p o p u l a t i o n and combinations of chemical w i t h nonchemical pest c o n t r o l methods.


The report a l s o stated that i n 1971 about 4,500,000 persons i n the U.S. on an average were engaged i n farm employment and that about 8,000,000 to 9,000,000 probably do some work i n commercial a g r i c u l t u r e . Although the annual average f i g u r e f o r farm employment had f a l l e n to about 3,800,000 (6) i n 1979, a c o n s i d e r a b l e number of persons may be exposed to p e s t i c i d e s by reason of t h e i r employment or involvement i n a g r i c u l t u r e . I t i s d i f f i c u l t to o b t a i n f i g u r e s that a c c u r a t e l y r e f l e c t the incidence of p e s t i c i d e poisoning, and the number of documented cases of d i r e c t human poisoning i n the USA v a r i e s from source to source. I t was estimated that there are 100,000 n o n f a t a l cases of human poisoning each year from p e s t i c i d e exposure ( 7 ) . In 1973 there were 1,474 cases of o c c u p a t i o n a l i l l n e s s a s s o c i a t e d with p e s t i c i d e exposure i n C a l i f o r n i a (8)· Organophosphate i n s e c t i c i d e s are a major cause of occupational poisoning. The F.W.G.P.M. Task Force addressed i t s e l f mainly to the problem of organophosphates, and i t s terms of r e f e r e n c e were t o i d e n t i f y areas i n which i n f o r m a t i o n on occupational exposure to workers was unavailable, to make recommendations f o r the development of research p r o t o c o l s to determine safe reentry l e v e l s f o r the p r o t e c t i o n of a g r i c u l t u r a l and f o r e s t workers, and to suggest i n t e r i m reentry standards based on e x i s t i n g knowledge. The report was c o n t r o v e r s i a l but drew a t t e n t i o n to the l a c k of a s u b s t a n t i a l data base and to the urgent need f o r s u r v e i l l a n c e of p e s t i c i d e - r e l a t e d morbidity and m o r t a l i t y and f o r research to i d e n t i f y f a c t o r s i n f l u e n c i n g safe worker reentry levels. The U.S.E.P.A. has concerned i t s e l f w i t h the problem of reentry i n t e r v a l s , and the q u a n t i t a t i v e measure of human exposure has become part of the RPAR ( r e b u t t a b l e presumption against r e g i s t r a t i o n ) process. U.S.E.P.A. requirements w i l l be promulgated as Subpart Κ of the g u i d e l i n e s f o r p e s t i c i d e r e g i s t r a t i o n under the t i t l e of "Reentry Data Requirements". D i f f e r i n g opinions concerning the value of g u i d e l i n e s have been expressed (WRCC-38) and a committee was c o n s t i t u t e d i n 1979 t o i n v o l v e the medical as w e l l as the a g r i c u l t u r a l community i n p e s t i c i d e residue research. One outcome of a seminar-workshop h e l d by that committee was an emphasis on minimizing human o c c u p a t i o n a l exposure. The seminar-workshop c l o s e l y preceded the current symposium ( 9 ) , and some of the c o n t r i b u t i o n s i n t h i s volume are focussed on the same areas.



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The i n c r e a s i n g amount of research data concerning p e s t i c i d e exposure i s to be welcomed: without t h i s , i t i s u n l i k e l y that there can be r a t i o n a l c o r r e l a t i o n s between exposure-related i l l n e s s and use of p e s t i c i d e s . M i n i m i z a t i o n of o c c u p a t i o n a l pesticide exposure can be attained by increased worker p r o t e c t i o n , changes i n p r a c t i c e or by reductions i n p e s t i c i d e use. In view of the unknown t o t a l burden of s y n t h e t i c chemicals among the p o p u l a t i o n at l a r g e , i t would seem prudent to minimize o c c u p a t i o n a l exposure. Regulatory a c t i o n s r e i n f o r c e standards and p r e s c r i b e safe operating c o n d i t i o n s . However, by seeking to reduce p o t e n t i a l exposure hazards to the worker, i n d i v i d u a l f a c t o r s such as personal hygiene, education, e t c . become l e s s significant. P e s t i c i d e use throughout the world i s i n c r e a s i n g and p r o t e c t i o n from exposure i s a world-wide problem. The problem i s i n t e r n a t i o n a l i n s c a l e and must be faced at that level. The d i f f e r e n c e s i n p e s t i c i d e use p a t t e r n s , c l i m a t i c c o n d i t i o n s and a t t i t u d e s to chemical p e s t i c i d e s among the nations of the world are so great that extreme d i f f e r e n c e s are to be expected i n the exposure s t a t u s of t h e i r p o p u l a t i o n s . Measures to safeguard the a g r i c u l t u r a l worker w i l l depend on i n t e r n a t i o n a l cooperation because a considerable amount of i n f o r m a t i o n must be exchanged. Operational g u i d e l i n e s must be supplemented by field studies of worker exposure and measurements of residue d i s s i p a t i o n i n the zone where a c t u a l use w i l l occur. Increased s e c u r i t y f o r workers and f o r the p o p u l a t i o n at large can only be achieved by adopting p r a c t i c e s and procedures which seek to minimize exposure. This goal may be achievable by good planning and management of pest c o n t r o l practices. I t s attainment a l s o r e q u i r e s the a v a i l a b i l i t y of considerable data t h a t must be provided by thorough a n a l y t i c a l , b i o l o g i c a l , and e p i d e m i o l o g i c a l i n v e s t i g a t i o n . The symposium papers r e f l e c t progress and discuss i s s u e s i n the United States i n r e l a t i o n to exposure of a g r i c u l t u r a l workers and, to a l e s s e r extent, of the community at l a r g e . However, the problem must u l t i m a t e l y be addressed on an i n t e r n a t i o n a l s c a l e .

Literature Cited 1.

Metcalf, R. L.

J. Agric. Food Chem. 1973,

2.

Bottrell, D. G. Integrated Pest Management Council on Environmental Quality, 1979. U.S. Gov. Printing Office, Washington, D.C. 20402, 3.

3.

Durham, W. F.

4.

Wolfe, H.R. and Durham, W. F., in: "Introduction to Crop Protection", W. B. Ennis, Ed., Amer. Soc. Agronomy and Crop Sci. Soc., Madison, WI, 1979, 304.

Ann. N.Y. Acad. Sci. 1969,

21, 511-519.

160,

183.



8

5.


6.

Federal Working Group on Pest Management. "Occupational Exposure to Pesticides. A Report to the Federal Working Group on Pest Management from the Task Group on Occupational Exposure to Pesticides". Washington, D.C., 1974. U.S. Dept. of Agric., Agricultural Statistics, U.S. Gov. Printing Office, Washington, D.C., 1980.

7.

Pimentel, D., B. Vinzant, D. Gallahan, D. Andow, T. E. Thompson, R. Dyson-Hudson, S. N. Jacobson, M. A. Irish, S. F. Kroop, A. M. Moss, and M. D. Shepard in: "Pest Control Cultural and Environmental Aspects", D. Pimentel and J. H. Per, Eds., AAAS Selected Symposium 43, Westview Press, Boulder, Colorado, 1980, 99-158.

8.

Yates, W. E. in "A Report on Seminar and Workshop in Pesticide Management", UC/AID Pest Management and Related Environmental Protection Project. Univ. Calif., Berkeley, 1975, pp. 63-71; cited by D. G. Bottrell in "Integrated Pest Management", Council on Environmental Quality, U. S. Govt. Printing Office, Washington, D. C., 1979, p. 13.

9.

Residue Reviews, 75, Springer Verlag New York Inc., New York, 1980.

RECEIVED

September 29, 1981.


Pesticide Residues and Exposure - ACS Publications - American

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